In general, a power transmission apparatus for an internal combustion engine having a supercharger attached thereto is constructed such that thermal energy included in exhaust gas discharged from a combustion chamber of the internal combustion engine via a turbine of the supercharger is recovered by a waste heat recovering turbine and power generated by the waste heat recovering turbine is transmitted to a crankshaft of the internal combustion engine thereby to increase an output from the internal combustion engine, and various proposals have been heretofore made as to the foregoing type of power transmission apparatus.
With respect to the foregoing type of conventional power transmission apparatus for an internal combustion chamber having a supercharger attached thereto wherein power generated by the waste heat recovering turbine is transmitted to the crankshaft of the internal combustion engine, one proposal is such that power generated by the waste heat recovering turbine is transmitted to the crankshaft of the internal combustion engine via an ordinary fluid coupling. Another proposal is made such that the waste heat recovering turbine is operatively connected to an associated unit via a speed reduction unit and an overrunning clutch and a power transmission apparatus including pulleys and a V-belt extending round the pulleys is operatively mounted on a shaft of the associated unit whereby power generated by a waste heat recovering turbine is transmitted to the crankshaft of the internal combustion engine via the power transmission apparatus.
Namely, with the above-described power transmission apparatus for an internal combustion engine having a supercharger attached thereto, the waste heat recovering turbine is normally connected to the crankshaft of the internal combustion engine via a power transmission passage therebetween.
It should of course be noted that with respect to the conventional power transmission apparatus for an internal combustion engine having a supercharger attached thereto, a part of power generated by the internal combustion engine is used directly as power for driving auxiliary units for a cooling system of the internal combustion engine so as to normally maintain the internal combustion engine in an operative state.
With the above-described conventional power transmission apparatus for an internal combustion engine having a supercharger attached thereto, a part of power generated by the internal combustion engine is consumed directly for driving an auxiliary unit for a cooling system of the internal combustion engine which requires the largest quantity of driving power among a plurality of auxiliary units for maintaining the internal combustion engine in an operative state. Thus, the conventional power transmission apparatus has a drawback that engine output is reduced because of the requirement for generated power.
In the case of a conventional internal combustion engine, usually, there is no need of forcibly cooling the engine in an operational region where the engine is rotated at a low speed or in an operational region where the engine is rotated under a low load. However, the conventional power transmission apparatus for an internal combustion engine having a supercharger attached thereto has a drawback that a large quantity of fuel consumption is normally required for continuously driving auxiliary units for a cooling system of the internal combustion engine even in an operational range where the engine is rotated at a low speed and/or under low load.
Further, with the conventional internal combustion engine having a supercharger attached thereto, due to the fact that a quantity of thermal energy included in exhaust gas delivered to the waste heat recovering turbine via a turbine in the supercharger is very small, few power is generated by the waste heat recovering turbine. However, since a conventional fluid coupling is used for the conventional power transmission apparatus for an internal combustion engine having a supercharger attached thereto, a part of power appearing on the crankshaft of the internal combustion engine is unavoidably consumed for driving the waste heat recovering turbine. Such useless work increases a quantity of fuel consumption. Particularly, in an operational region where the engine is rotated at a low speed, there arise problems that engine output is reduced and the engine has a degraded property of acceleration.
The present invention has been made with the foregoing background in mind and its object resides in providing a power transmission apparatus for an internal combustion engine having a supercharger attached thereto which assures that engine output, particularly, engine output in an operational region where the engine is rotated at a low speed can be increased and a quantity of fuel consumption in an operational region where the engine is rotated at a low speed as well as in an operational region where the engine is rotated under a low load can be reduced.